The use of bicarbonate and phosphate salts for the protection of agricultural and horticultural crops is well known. The most well known examples are potassium bicarbonate, sodium bicarbonate, ammonium bicarbonate and potassium phosphate, which are used on a large scale, especially in the US, for the control of fungal diseases.
A broad overview of the application of bicarbonate salts as fungicides is described in ‘Control of apple scab (Venturia inaequalis) with bicarbonate salts under controlled environment’, L. Jamar, B. Lefrancq & M. Lateur; Journal of Plant Diseases and Protection, 114 (5), 221-227, 2007, ISSN 1861-3829. Although the use of bicarbonate salts as an additive in food products is known, the application in controlling plant diseases has been limited. Bicarbonates have proven their activity in the control of a broad range of fungi, amongst others fungi that occur on food products, and in controlling plant pathogens. The activity of sodium bicarbonate in the control of mildew on cucumber is described, adding of surfactants seems to improve the activity against green fungus on citrus. It is explained that calcium hydroxide is capable of preventing the germination of spores and killing the spore sacks (asci) of apple scab (V. inequalis) in a concentration of 4.3 g/l. Potassium bicarbonate seems to be effective in decreasing fruit and leaf scab. The use of sodium bicarbonate as such or in combination with a reduced dose of tebuconazole for controlling apple scab in practical circumstances is mentioned. Besides this, other fungal diseases such as mildew, Alternaria, Anthracnose, Botrytis, . . . are described. Also the activity of watery solutions of bicarbonates mixed with vegetable or mineral oils in the control of apple scab is discussed.
The exact mechanism of how these salts operate is however not yet known. Different theories are described in which it is accepted that the salts cause a change in the pH of the leaf surface, or cause a damage of the cell wall membrane of the fungal spores as a result of which the spores dry out and die, or cause a disequilibrium between the K- or N-ions in the fungal cells as a result of which the cell wall bursts open.
The use of carbonate salts and further also phosphate salts as insecticides is also mentioned in a number of different publications.
JP 5039206 describes the use of a water-soluble powder of carbonates, bicarbonates, phosphates and sulphates for controlling aphidoidea such as aphids and acarina such as mites and ticks.
In the “Pakistan Journal of Botany”, vol. 35, nr. 5, 2003 the use of KH2PO4 is described for controlling Bemisia tabaci and white flies.
In “Turkiye Entomoloji Dergisi” vol. 26, nr. 2, September 2002, the use of sodium bicarbonate is described for controlling aphids, white flies, and red spider mites in greenhouses.
In the “New Zealand Journal of Crop and Horticultural Science” vol. 27, nr. 2, the use of sodium bicarbonate is described for controlling larvae of Epiphyas postvittana Walker.
The “Queensland Journal of Agricultural and Animal Sciences”, 1969, 26 (1), 83-8 describes the use of a white mixture of oil, soap and disodium carbonate for controlling white lice (Unaspis citri) and the Maori mite (Phyllocoptrutua oleivora).
WO 2004/056184 A1 describes the use of a powder comprising 40% wt. of sodium bicarbonate for use as an insecticide, more specifically as an acaricide and also as a fungicide in storage rooms for cereals, such as for example silos.
WO 94/00982 describes a pesticide composition comprising an inorganic salt chosen from alkali metal and ammonium bicarbonates, and an ingredient chosen from C8-C22 fatty acids, and salts thereof. This pesticide is described for use as a fungicide, herbicide and insecticide, without mentioning specific species of harmful organisms. The composition can be used for agricultural and horticultural applications, and as a shampoo for pets.
WO 89/10693 describes a method for protecting plants against phytophagous arthropods whereby a watery solution is applied, on the plant, of a composition comprising a monocarboxylic acid with 8-20 C-atoms, or salts thereof, with an agent for sequestering metal ions. As such an agent, phosphate salts are mentioned. This method is described against for example mites, aphids and white flies.
None of the previous publications however describes the use of the respective compositions comprising carbonate- or phosphate salts for controlling insects of the superfamily of the Psylloidea. Nonetheless, insects of this family, such as Pear Psylla, are an important threat for a great number of crops. Moreover, many known pesticides often have a minor or insufficient effect with respect to insects of this family.
EP 0322583 A1 describes an insecticide composition for controlling Pear Psylla, wherein the composition comprises an alkali-metal dioctyl-sulpho-succinate as an active ingredient. Besides this, the composition comprises a salt mixture with a buffering effect. As a salt mixture with a buffering effect, amongst others a phosphate buffer, a phthalate buffer, a citrate/phosphate buffer and a tartrate/phosphate buffer are mentioned.
WO 98/38867 describes a method for controlling arthropods whereby a certain quantity of a particle-shaped material is applied chosen from a large group of amongst other calcinated kaolins, hydrophobic calcinated kaolins, and hydrophobic calcium carbonates. This method is described for a large number of arthropods, such as insects, mites and spiders. More specifically, this method can be used against crawling, jumping, or flying arthropods. In example III, Pear Psylla is mentioned. The method relates to a physical plant protection product. Hereby the particle-shaped components are not soluble in water, as a result of which they do not control the arthropods mentioned as an active ingredient. By creating an environment containing these particle-shaped materials, a hostile environment for the arthropods is created, as a result of which these will be repelled such that they will not feed, and will not lay eggs. There is however no chemical interaction between the arthropods and the particle-shaped material, as a result of which they are not killed in a direct manner.
The compositions and methods described here above describe the control of insects of the superfamily of the Psylloidea, but offer an insufficient effectiveness in this control.
Other existing chemical insecticides with a broader action range which for example exert an altering function in the insect metabolism, have an insufficient effectiveness against insects of the superfamily of the Psylloidea, and are moreover often harmful for humans and the environment.
Given that lots of agricultural and horticultural products, more specifically seed fruit, for example apples and pears, are intended for both direct consumption by humans and animals whereby often not only the fruit pulp but also the outer peel is consumed, but which are also consumed as processed or prepared products, there is a need for a means for effectively controlling insects of the superfamily of the Psylloidea, which means has a low toxicity for the consumer and a low ecotoxicity and is more efficient than the existing pesticides for Psylloidea. It is after all also known that some insecticides and fungicides which are applied onto the peel do protrude into the pulp to a certain extent and often can not entirely or unsufficiently be removed from the peel by washing. Moreover there is a need for such a pesticide in which the risk for the development of resistance by the insects and parasites is strongly decreased.